Biodiesel is a diesel replacement fuel for compression-ignition (CI) engines and is a legally registered fuel and fuel additive with the U.S. Environmental Protection Agency (EPA). The EPA registration includes all biodiesel that meets the ASTM specification ASTM D 6751 and such standards do not depend on the oil or fat used to produce the biodiesel or the specific production process employed.
The biodiesel manufacturing process converts fats and oils into chemicals called long-chain mono-alkyl esters or biodiesel. These chemicals are also referred to as fatty acid methyl esters (FAME). The term mono-alkyl ester indicates that biodiesel contains only one ester linkage in each molecule.
Fats and oils are composed principally of triglycerides made up of a glycerol moiety in which the hydroxyl groups are esterified with carboxylic acids. Whereas solid fats tend to be formed by triglycerides having saturated fatty acids, triglycerides with unsaturated fatty acids tend to be liquid (oils) at room temperature. Monoglycerides and diglycerides, having respectively one fatty acid ester and two alcoholic groups or two fatty acid esters and one alcoholic group, are also found in fats and oils to a lesser extent than triglycerides.
Biodiesel is produced through a chemical reaction of a triglycerides (TG) or free fatty acids (FFA) with an alcohol, such as methanol, to form an alkyl ester. Free fatty acids, which are found in degraded oils such as FOG, can be converted to esters using an acid catalyst. Triglycerides can be converted using an alkaline catalyst. In the alternative, conversion of both free fatty acids and triglycerides may be effected with enzyme catalysis by using lipases obtained from microorganisms including but not limited to Rhizomucor miehei, Rhizopus species, Aspergillus niger, Candida cylindracae, Candida antartica, Thermomyces Lanuginosa, Pseudomonas species, Arthrobacter species, etc.
Also included in the grouping for conversion to biodiesel are recycled greases, such as cooking oils and restaurant frying oils. Grease is a material, either liquid or solid, composed primarily of fats, oils and grease (also referred to as FOG) from animal or vegetable sources. Yellow grease is oil and grease that comes directly from fryers and other cooking equipment. Trap grease or brown grease is waste that is recovered from grease traps and interceptors. A grease trap is a small volume device located inside a food service facility, generally under a sink, designed to collect, contain, or remove food wastes and brown grease from the waste stream while allowing the balance of the liquid waste to discharge into the wastewater collection system, usually a sanitary sewer system. A grease interceptor is a large volume device located underground and outside of a food service facility designed to collect, contain or remove food wastes and brown grease from the waste stream while allowing the balance of the liquid waste to discharge to the wastewater collection system, usually a sanitary sewer system.
Recognizing the negative effects of fats, oil and grease on sewer systems and/or waste water treatment plants, it is important to inhibit the FOG from entering into wastewater collection systems and/or landfill sites. Communities, counties, and water districts are grappling with the issue of how best to handle grease trap wastes. Most wastewater treatment plant managers feel that from a technical point of view, it is best to have regulations requiring restaurants to have grease traps pumped regularly, and to have the waste discharged at wastewater treatment plants where it can be properly treated and disposed of. Thus, there are grease trap pumping companies that collect the waste and deliver to facilities that can convert grease to inert solids or convert to useable materials such as biogas, biodiesel, biological fertilizer, etc.
Importantly the FOG in the grease traps can include emulsified FOG which cannot be easily floated off the surface. Spent FOG is 10 to 15 percent lighter than water and will float to the surface of liquid medium in a container if not emulsified. Emulsification is the term given to the condition when spent FOG does not separate from water. This is a concern because emulsification allows spent FOG to pass readily through grease traps to enter other systems. Thus, a separation method must consider a system that entraps any emulsified FOG.
In light of the above discussion, there is a need for purification and production systems that efficiently provide for producing biodiesel fuels and other valuable components from trap oils, trap greases, brown greases, yellow grease and grease trap waste while producing a minimal amount of negative effects on sewer systems, wastewater treatment facilities and/or landfill sites.